It is often necessary in domestic and construction applications to repair or upgrade a section of pipe for conveying fluid around a system. For example, it may be necessary to repair a ruptured section of pipe or to fit a valve mechanism along a section of pipe close to a component in a system that is to be serviced and does not have its own isolation valve. Generally, it has in the past been necessary to shut off the fluid supply upstream of the section of pipe. This may be problematic since it may not always be possible or convenient. For example, an upstream isolation valve may be jammed open, may be leaking, or may be remote from the location of the section of pipe and may undesirably prevent fluid flow to other locations. Furthermore, isolating the fluid supply upstream of the section of pipe will not prevent residual fluid downstream of the isolation valve from undesirably leaking from the section of pipe when removed with consequential loss of fluid.
There exist means by which pipes may be frozen to form an “ice plug” to allow maintenance of a system to take place downstream of the plug. However, this method is only suitable for fluids such as water that can be frozen easily and does not lend itself to fluids such as gas or oil. Furthermore, it can take some considerable time to form the plug and to thaw the plug for system testing or operation to subsequently take place after maintenance is completed. Although techniques for cutting sections of pipe have been proposed without isolating the fluid supply, to the present applicant's knowledge, none of the techniques proposed have been successfully adopted to date. Examples of such prior art include U.S. Pat. No. 3,687,166 and U.S. Pat. No. 1,989,768.
U.S. Pat. No. 3,687,166 discloses a control valve that is configured to be introduced into a pipe filled with fluid, the control valve comprising an assembly configured to move linearly to slice through the pipe during installation and, in use, form a linear gate valve for sealing against a split gasket to isolate flow through the pipe.
U.S. Pat. No. 1,989,768 discloses apparatus for inserting a valve into a pipe, the apparatus comprising a sealable housing containing a pipe cutter for cutting a section of pipe and assembling a pair of slidable flanges about the pipe for receiving a valve after the cut section of pipe has been removed. The valve is sealably coupled to the pipe by connecting flanges located on the valve with the slidable flanges assembled about the pipe.